A MEMS micro-mirror device is a device that contains an optical MEMS (Micro-Electrical-Mechanical-System). The optical MEMS may comprise a cylindrical, rectangular or square micro-mirror that is adapted to move and to deflect light over time. The micro-mirror is connected by torsion arms to a fixed part and can tilt and oscillate along one or two axis. For example, the micro-mirror can oscillate vertically and horizontally. Different actuation principles can be used to tilt and oscillate the micro-mirror, including electrostatic, thermal, electro-magnetic or piezo-electric. MEMS devices are known in which the area of these micro-mirrors are around a few mm2. In this case, the dimensions of the MEMS device, comprising the packaging, is around ten mm2. This device is usually made of silicon, and can be encapsulated in a package that can include the driving actuation electronics. Various optical components, such as for example, lenses, beam combiner, quarter-wave plates, beam splitter and laser chips, are assembled with the packaged MEMS to build a complete system.
A typical application of the micro-mirror devices is for projection systems. In a projection system, a 2-D, 3-D image or a video can be displayed on any type of display screen: each pixel is generated by combining modulated red, green and blue laser light sources, by means of, for example, a beam combiner. A MEMS micro-mirror device directs this beam of light to a display screen and reproduces the image, or the video, pixel-by-pixel. By means of its oscillations, the micro-mirror within the device will continuously scan light from left to right and/or right to left and from top to bottom and/or from bottom to top of the display screen so that each pixel of the 2-D image or video is displayed on the display screen.
For optimal image quality each pixel projected by the projection system should be circular. However, circular pixels are difficult to achieve since the projected light source diverges; in particular, the projected light source diverges an unequal amount along both the horizontal x-axis and vertical y-axis. Accordingly, the pixels projected on the display screen will be oval rather than circular in shape.
It is an aim of the present invention to obviate or mitigate at least some of the above-mentioned disadvantages.